1. Field of the Invention
The present invention relates generally to an earphone jack for improving a call quality in a mobile communication terminal, and an operating method thereof. More particularly, the present invention relates to an earphone jack for eliminating power noise interference in a voice call, thereby improving a signal-to-noise ratio (SNR), and an operating method thereof.
2. Description of the Related Art
In general, an earphone is a device for allowing a user to hear a media sound source signal from a media-recording media, a mobile communication terminal, wireless broadcasting, or the like. The earphone apparatus has been advanced in various product areas such as those related to headphones for use convenience, and is further being advanced to provide increased use ranges. The earphone is applied to the mobile communication terminal to allow the user to hear a call voice signal from a counterpart, as well as to hear a media sound source signal.
In a typical application, the user holds and uses the mobile communication terminal in his/her hand in the same manner as a telephone. When the user drives a car, he/she can connect the earphone to the mobile communication terminal and can then easily communicate with the counterpart without holding the mobile communication terminal in his/her hand. Accordingly, the earphone can be easily connected to a device such as an MPEG layer-3 (MP3) phone and used for allowing the user to hear MP3 data from the MP3 phone, and can also be used for transmitting and receiving data in the mobile communication terminal.
FIG. 1 is a view illustrating a conventional earphone jack and earphone included in a mobile communication terminal.
In FIG. 1, the earphone 110 is electrically coupled with the earphone jack 100, thereby outputting an audio signal from the mobile communication terminal through both speakers 112 and 114 of the earphone 110. In general, the earphone jack 100 includes a total of five terminals comprising microphone bipolar terminals, speaker bipolar terminals, and a ground single-pole terminal. However, for clarity in the description of the earphone jack 100 of FIG. 1, only the speaker bipolar terminals 102 and 106, and the ground single-pole terminal 104, are illustrated, as these result in many of the problems solved by the embodiments of the present invention, and the microphone bipolar terminals are not illustrated.
In the earphone jack 100 of the mobile communication terminal of FIG. 1, the speaker bipolar terminals 102 and 106 output a call voice signal in a call mode, and a media sound source signal (for example, an MP3 media sound source signal) from a sound source recording media. An output format of the speaker bipolar terminals 102 and 106 can be comprised of a mono sound format (that is, the same call voice signal) that is output to the speaker terminals of both sides, and a stereo sound format (that is, media sound source signals different from each other) that is output to the speaker terminals of both sides.
When the media sound source signal is output in stereo, the mobile communication terminal outputs a regular electric power level of a power source and therefore, the media sound source signal can be stably output, almost without any influence of power noise. However, when the call voice signal of the call mode is output, there is a drawback in that when a voice call is performed, power noise is generated at the earphone 110 and therefore, a clear voice signal without power noise cannot be output.
Specifically, a time duration (hereinafter referred to as an “awake time”) for transmitting and receiving a wireless signal at a predetermined time interval is required for setting a connection link or maintaining a call state between a mobile communication base station and the mobile communication terminal. During the awake time, an electric power level of a battery is required for transmitting and receiving the wireless signal. For example, in a time division multiple access (TDMA) mobile communication system, such as a global system for mobile communications (GSM) mobile communication system, the mobile communication terminal wirelessly communicates in the call mode with the mobile communication base station only during its allocated driving time duration (that is, the awake time). Therefore, electric power is consumed to a greater extent during the awake time than during other times.
An electric power waveform, which is output when the electric power of the battery is consumed during the awake time, is shown in FIG. 2. During the awake times of 202a, 202b, 202c, and 202d, the battery is consumed and an output reduced by about 0.4V. For example, in the mobile communication terminal, the battery outputs a voltage of 4.2V at other times, but during the awake times, the battery is consumed and an output reduced by as much as about 0.4V. This consumption and output reduction is the result of performing a wireless link with the base station. Therefore, the battery outputs a voltage of 3.8V, which is lower by as much as 0.4V than the 4.2V output at other times.
Accordingly, while the call voice signal of the mono sound format is output in the call mode through the left and right speakers 112 and 114, power noises 212a, 212b, 212c, and 212d, and power noises 222a, 222b, 222c, and 222d, are respectively generated in a voice output waveform 210 of the left speaker terminal 104 and a voice output waveform 220 of the right speaker terminal 106 at a corresponding awake time, due to the electric power consumed during the awake time taken to perform wireless communication.
Power noise refers to noise interference in the call voice signal when a battery output is not stably provided and a low electric power level is output during a specific time duration. When the electric power is not supplied normally, power noise causes noise interference in an analogue voice signal waveform. Accordingly, there is a drawback in that when the voice call is performed, optimum call quality cannot be provided for a terminal user due to power noise interference in the call voice signal.
Accordingly, a need exists for a system and method for eliminating power noise interference in a voice call during the awake time taken to perform wireless communication.